Method for the formation of connection sleeves

ABSTRACT

A method and an apparatus are disclosed for manufacturing a sleeve like article, having similar sleeve like branches connected thereto, such as for example portions of a motorbicycle frame, by resistance welding along a generating line of a stamped out blank. The stamped out blank is properly bent and housed between two clamps which embrace the bent blank for at least two fifths of its overall surface and rest on the surfaces of the branched off sections for at least one fifth of the surface of the latter.

United States/Patent n91 -Agrati June 4, 1974 [54] METHOD FOR THE FORMATION OF I 1,864,139 6/1932 Mark 219/65 CONNECTION E S 1,924,915 8/1933 Cutter 219/65 [75] Inventor: Franco Agrati, Monticello Brianza,

ltaly Primary Examiner-11. V. Truhe Assistant Examiner-Hugh D. Jaeger [73] Assignee. ggl'all Garelll S.p.A., Monticello Attorney Agent, or Firm Hill, Sherman Memni,

ianza, Italy Gross & Simpson [22] Filed: Mar. 8, 1973 [21] Appl. No.: 339,276

[57] ABSTRACT [30] Foreign-Application Priority Data A method and an apparatus are disclosed for manu- Mar. 18. 1972 Italy 22088/72 f t i g a sleeve like article, having similar sleeve like branches connected thereto, such as for example [52] US. Cl 219/67, 29/4743, 219/67, portions f a motor bicycle frame, by resistance we]d 285/286 ing along a generating line of a stamped out blank. 7 [51] Int. Cl B23k 31/06, B2ld 39/04 The Stamped out blank is properly bent and housed [58] new of Search 219/64 67; 29/4743; betweentwo clamps which embrace the bent blank for v 285/286 at least two fifths of its overall surface and rest on the surfaces of the branched off sections for at least one [561 References cued fifth of the surface of the latter.

UNITED STATES PATENTS 1,816.864 8/1931 Murray 219/65 6 Claims, 7 Drawing Figures METHOD FOR THE FORMATION OF CONNECTION SLEEVES tape. This developed surface is stamped and folded to form the sleeve: more particularly in curlingthe main sleeve can be shaped by closing the metal sheet by bending about the generating lines thereof: in such a way the sleeve must be welded along a generating line of its own. If it is desired to provide a main sleeve from which a secondary sleeve branches off, care should obviously be taken so that the generating line to be welded on the main sleeve is the one which intersects the axis of the sleeve connected thereto: it is obvious that in such a way the secondary sleeve is formed by two discrete halves and then soldered ating lines.

A shaping operation of the kind referred to above can also be practiced when a main sleeve has several secondary sleeves connected thereto all of them with an axis intersecting the same generating line of the main sleeve.

The welding of the workpiece, after bending, can be along two genercarried outwith different methods all of which provided for the use of added material, such as for example blowpipe welding, electric welding and so on.

These methods require along time for being carried out and are thus expensive: in addition the'performance of the hand welding is entrusted to the operator's skill. If one takes into account that the thickness of the material is comparatively small and that the welding seam should be machined to obtain for the sleeve an outer surface deprived of discontinuities, it is apparent that only an absolutely perfect welding could assure a sufficient sealtightness and resistance to the finished piece.

The object of the present invention.is to provide a method for welding sleeve bodies, more particularly for connections as defined above, which is extremely quick and whose performance is accurate and reliable.

It has been surprisingly found that it is possible to provide a closed-cross-sectional sleeve body by welding its wall in correspondence with a generating line, by using the resistance welding technique. Generally, resistance weldinghas found applications in the union of two discrete bodies intended to make up a single member: at the most, it has found an application in butt-welding in a closed loop of elements having a high length so that these latter had a high electric resistance and the current clamps are applied in the vicinity of the ends to be jointed.

According to the invention, this method has been applied to welding of sleeve bodies formed by bending a metal sheet, favourable results being obtained, which cannot be achieved with the conventional art.

The method according to the invention for the formation of a closed cross-section member of the kind of a sleeve, more particularly one comprising a principal body to which secondary sleeve members are connected, said member consisting of a developed surface traced on a metal sheet and bent so as to form with its central portion the principal body as open along a generating line and to form, with its peripheral portions said secondary member open along two generating lines, said method comprising the step of housing the thusly bent developed surface between two clamps which rest there against in correspondence with the side surface of said principal body, in the vicinity of said open generating line, on an area of not less than two fifths and not exceeding four fifths of the total surface area thereof, and rest in correspondence with the surfaces of said secondary body on an area of not less than one fifth of the total surface area thereof, and of approaching said clamps placed under electric tension and carrying out the electric resistance welding in correspondence with the open generating lines aforesaid.

ber, such as embodied according to the invention.

FIG. 2 shows a side view of the member shown in FIG. 1.

FIG. 3 shows a partial view of the welding apparatus.

FIGS. 4 and 5 show cross-sectional views taken along the lines IVIV of FIG. 3 for different positions of the apparatus.

FIGS. 6 and 7 show cross-sectional views taken along the line VIVI of FIG. 2, for different processing stages of the workpiece.

. As has been depicted in FIGS. 1' and 2, the component part to be fabricated comprises a main portion 10 having the form of a sleeve, to which secondary bodies i 11 and 12 are connected: the article has its surface made of stamped sheet metal which has been bent according to a method well known to those skilled in the art. After having been shaped by bending, the piece requiresa longitudinal welding which is extended along the generating line 13 of the body 10, along two generating lines 14 of the body 11 and along two generating lines 15 of the body 12.

As has been shown in FIGS. 3 and 4, the article is placed between two'clamps 16 which partially mate the outer surface of the article so as to rest continuously on the bodies 11 and 12 and partially on the central body 10: for the sake of clarity of showing in the drawings, FIG. 3 does not show either of the two clamps l6 and the member 10-11-12 has been shown in dash-and-dot lines. A pad 17' presses, in a contrallable manner, the body 10 towards the clamps 16 and is brought to 18 by a lever 19 pivoted at 20.

The clamps 16 are connected through lines to a source of electric power 30 of the kind as conventionallyused in electric resistance welding machines and can controllably be moved the one towards the other.

FIG. 4 shows in cross-sectional view the body 10 as has been housed between the clamps after shaping by stamping and bending of the sheet metal which forms which are placed in mutual contact by approaching the clamps 16 is such as to melt the edges for adequate power values. It has been seen that values of the power which are adapted for a satisfactory welding do not impair the back of the body 10, that is, in correspondence with its portion which is clear of the clamps l6. Welding the bodies 11 and 12 does not offer any special difficulties since they are made in two halves as it is customary in the pieces shaped by resistance welding. In order better to clear the progress of the welding operation in H6. 5, there is shown the arrangement of the clamps 16 at the termination of the welding step in correspondence with the f generating line 13. Likewise, FIGS. 6 and 7 show, before welding and after welding, respectively, the appearance of the cross-section of the body 12: the appearance of the body 11 would be quite similar.

It has been shown that the shaping of the workpiece such as shown therein is extremely advantageous as to the time required and the reliability of processing.

In addition, the method according to the invention enables the welding to be effected by resistance for a piece having a closed cross-section but open along one generating lineonly: this involves an immediate advantage in the finishing of the piece, which obviously is required for a single welding seam. If the pieces is intended to form a portion of a frame, the welding seam can be conveniently made in the less exposed portion.

It should be noticed that the apparatus and the method as shown are subjected to a number of changes, without thereby departing from the scope of the present invention. More particularly, the pieces which can be shaped are of extremely variable types and the clamps will have suitable hollow spaces for displacing been shown as they are extended along the body 10 substantially in the immediate vicinity of the welding seam, to a generating line which is distant from the welding seam through an arc subtended by a substantially right angle, as clearly shown in FIGS. 4 and 5.

However, the clamp can encompass a lesser area of the body, or also a greater area. ln the latter case it is apparent that it encompasses the body 10 by holding it, so that the presser pad 17 is redundant.

lt has been shown in practice that the contact surface between the clamps l6 and the body 10 can have an area which is a fraction comprised between two-fifths and four fifths of the total area of the body 10 concerned.

Much less of importance is the magnitude of the surface area between theresting surface for the clamps on the secondary bodies 11 and 12 which are composed by two half-shells. More particularly the area could be substantially the entire area of the surface, as shown, or one fraction thereof only, which is extended from the area in the vicinity of the welding seam. For a satisfactory electric contact it is recommended, at any rate, that said fraction exceeds one fifth of the surface.

It is quite clear that a certain portion of the sheet metal, in correspondence with the edge to be welded, is intended to soften and form the welding seam. The

the outer surface of the workpieces. The clamps have sheet metal developed surface intends to form the article should thus have an excess of material in that area. In order to obtain a circular cross-section for the bodies l0, l1 and 12 it is thus necessary to start from an elliptical section such as shown in the drawings.

With the method according to the invention, sleeve members can be obtained with an extremely wide variety of shapes and more particularly can be easily matched with planar clamps those articles in which the axes of a plurality of secondary bodies intersect, all, the same generating line of the main body.

What is claimed is:

1. A method for the formation of anarticle having a closed cross-section of the sleeve type, more particularly comprising a main body to which secondary sleeve bodies are connected, formed by a stamped out developed surface of sheet metal which is bent to form with its central portion said principal body open along a gen-- erating line and to form with its peripheral portions said secondary bodies open along two irregularly shaped generating lines, said method being characterized in that it comprises the step of housing said thusly bent developed surface between two movable clamps which rest thereon in correspondence with the side surface of said main body in the vicinity of said open generating line, on an area not less than the 2/5ths and not exceeding the 4/5 ths of the total area thereof, and rest in correspondence of the surface of said secondary bodies on an area of not less than one fifth of the total area thereof and subsequently the operation of approaching said clamps maintained at different voltages by a source of electric power, effecting the resistance electric welding in correspondence with said open irregularly shaped generating lines.

2. A method according to claim 1, characterized in that said main body housed between said clamps is pressed by a pressural member in correspondence with the generating line opposite to the open generating line aforesaid when said clamps are driven to approach one another.

'3. A method according to claim 1, characterized in that said clamps are driven to approach one another in a direction substantially tangential to said main body in correspondence with said open generating line.

4. An apparatus for the formation of a closed-crosssection article of the sleeve type, more particularly comprising a main body to which secondary sleeve bodies are connected, formed by a stamped out sheet metal developed surface which has been bent to form with its central portion said main body open along a generating line and to form with its peripheral portions said secondary bodies open along two generating lines, said apparatus being characterized in comprising two movable clamps adapted to receive said developed surface by resting thereon in correspondence with the lateral surface of said main body, in the vicinity of said open generating line, on an area of not less than two fifths and not more than four fifths of the total area thereof, and resting in correspondence with the surfaces of said secondary bodies on an area of not less than one fifth of the total area of said bodies, means for moving said clamps from a distal position where they receive said member and a proximal position where they mutually press the edges of said developed surface corresponding to said open generating line, a source of electric power connected to said clamps to maintain at different potentials when they are moved from said 6 position to said proximal position;

6. An apparatus according to claim 4, characterized in that said clamps rest on the surface of each of said 5 secondary bodies, the edges corresponding to their open generating lines remaining projecting therefrom. l= 

1. A method for the formation of an article having a closed cross-section of the sleeve type, more particularly comprising a main body to which secondary sleeve bodies are connected, formed by a stamped out developed surface of sheet metal which is bent to form with its central portion said principal body open along a generating line and to form with its peripheral portions said secondary bodies open along two irregularly shaped generating lines, said method being characterized in that it comprises the step of housing said thusly bent developed surface between two movable clamps which rest thereon in correspondence with the side surface of said main body in the vicinity of said open generating line, on an area not less than the 2/5ths and not exceeding the 4/5 ths of the total area thereof, and rest in correspondence of the surface of said secondary bodies on an area of not less than one fifth of the total area thereof and subsequently the operation of approaching said clamps maintained at different voltages by a source of electric power, effecting the resistance electric welding in correspondence with said open irregularly shaped generating lines.
 2. A method according to claim 1, characterized in that said main body housed between said clamps is pressed by a pressural member in correspondence with the generating line opposite to the open generating line aforesaid when said clamps are driven to approach one another.
 3. A method according to claim 1, characterized in that said clamps are driven to approach one another in a direction substantially tangential to said main body in correspondence with said open generating line.
 4. An apparatus for the formation of a closed-cross-section article of the sleeve type, more particularly comprising a main body to which secondary sleeve bodies are connected, formed by a stamped out sheet metal developed surface which has been bent to form with its central portion said main body open along a generating line and to form with its peripheral portions said secondary bodies open along two generating lines, said apparatus being characterized in comprising two movable clamps adapted to receive said developed surface by resting thereon in correspondence with the lateral surface of said main body, in the vicinity of said open generating line, on an area of not less than two fifths and not more than four fifths of the total area thereof, and resting in correspondence with the surfaces of said secondary bodies on an area of not less than one fifth of the total area of said bodies, means for moving said clamps from a distal position where they receive said member and a proximal position where they mutually press the edges of said developed surface corresponding to said open generating line, a source of electric power connected to said clamps to maintain at different potentials when they are moved from said proximal position.
 5. An apparatus according to claim 4, characterized in that it comprises a pressure member controlled so as to act on said body in correspondence with the generating line of the main body opposite to its open generating line, when said clamps are moved from said distal position to said proximal position.
 6. An apparatus according to claim 4, characterized in that said clamps rest on the surface of each of said secondary bodies, the edges corresponding to their open generating lines remaining projecting therefrom. 